There is food processing apparatus of the type broadly set forth above having a working bowl or vessel with a motor-driven shaft projecting vertically upwards through the bottom of the bowl on which various selected rotary tools can be engaged to be driven by the shaft for performing various food processing operations as may be desired by the user. A detachable cover is secured over the top of the bowl during use. This cover includes a hopper or feed tube which has a mouth that opens downwardly through the cover into the top of the bowl. The food items to be prepared are placed in this feed tube and then are manually pushed down through the feed tube into the bowl by means of a removable pusher member which is adapted to slide down in the manner of a plunger into this feed tube. For further information about this type of food preparing apparatus the reader may refer to U.S. Pat. No. 3,892,365 - Pierre Verdun.
The rotary tools include cutting discs, slicing discs, rasping discs, grating discs, etc. which have a disc-like cutting tool member formed of sheet metal, preferably stainless steel, with one or more cutting elements projecting above the upper surface of the cutting disc member. These tools which have a disc-like cutting member are intentionally positioned in the top of the bowl near the lower surface of the cover where they can cut, slice, rasp or grate the food items entering downwardly from the feed tube into the top of the bowl. For the purpose of positioning the disc-like cutting tool member in the top of the bowl, the rotary tool includes a relatively long hollow hub extending relatively far down into the bowl. This hollow hub slides vertically down around the upper end of the motor-driven shaft. In order to provide a driving connection between the shaft and this hollow hub, the shaft is formed with driving coupling means, such as a flat face or keyway on one side, and the hollow hub has complementary coupling means, such as internal lugs or keys, for engaging the shaft.
As examples, the food items to be sliced or cut may be such as, cucumbers, carrots, cabbage, onions, potatoes, raddishes, squash, peppers, celery, turnips, parsnips, beets. Food items to be rasped or greated may be such as cheese, carrots, potatoes, cabbage and lemons.
In some cases in using the prior art tools which have such a disc-like cutting member the user may become so intent upon processing the food items as not to notice that the bowl beneath the cutting member has become full of the processed food. In such cases the user may continue to process food until finally the bowl becomes so full that the food forces the disc-like cutting member of the rotary tool upwards against the lower surface of the cover.
In this type of food processing apparatus the rotary tool is usually driven at a speed in the range from 1,000 revolutions per minute (RPM) to 2,000 RPM, and the electric driving motor is relatively powerful so that it cannot readily become stalled. Consequently, when the disc-like cutting member becomes forced up against the cover, it can scratch or scour the cover as well as dull the tool. The cover is usually made of rigid transparent plastic for convenient observation of the processing operation. The scratching or scouring of the lower surface of the cover thereafter makes difficult the observation of food processing. Also, the roughened cover surface is much harder to clean than the original glass-like smoothness of the rigid plastic.
In other cases in using these prior art rotary tools, the user may become overly enthusiastic or too vigorous in forcing the food item, such as cheese or carrots, down through the feed tube. The result is to depress the sector of the disc-like cutting members where the food item is being pressed down upon it. In extreme cases the opposite sector of the cutting member becomes deflected up against the lower surface of the cover, again causing a scratching or scouring of the cover and a dulling of the rotary tool.
In prior art rotary tools a small central raised button has been provided at the hub, but such a central button has not prevented the deflection of the disc-like cutting member up against the cover in either manner as described above.